This invention relates to electromagnetic valves, such as for engines, and, more particularly, to valves with motion controlling restraint devices for slowing the opening and closing of such valves.
Electromagnetic valve actuators for use in engines typically feature an engine valve connected to an armature that is spring-centered between two electromagnets. Other prior electromagnetic valve actuators featured an opening coil cooperative with a closing spring. In either case, the armature is induced to move between a xe2x80x9cvalve closedxe2x80x9d position where the valve head engages a valve seat and a xe2x80x9cvalve openxe2x80x9d position where the valve engages a stop. Where movement of the armature between the open and closed positions, remains uncontrolled, however, the impact of the moving armature on the stop and valve seat respectively, not only causes wear on the stop and/or valve seat, but also causes audible valve train noise.
The present invention provides a motion controlling restraint for slowing a reciprocating valve in an electromagnetic valve actuator. The restraint is operable on a follower connected to the valve, to slow valve motion and reduce the force of engagement of the valve with the seat and stop as the valve approaches its open and closed positions respectively. The restraint of the present invention may include either hydraulic or mechanical devices.
The hydraulic restraint device of the present invention includes a hydraulic piston, which is coupled to the valve stem and is reciprocable between two fluid-filled hydraulic chambers of a cylinder. The chambers are connected by a bypass passage at locations spaced from their ends. The chambers are further connected at their ends by a restrictive flow tube. As the electromagnetic coils within the actuator energize and de-energize, the hydraulic piston moves accordingly, blocking fluid flow through one or more ports of the bypass passage and forcing it into the flow tube. Hence, flow through the bypass passage is regulated by the positional relationship of the hydraulic piston to the bypass passage. The passage size and the size and shape of the port openings between the bypass passage and the two hydraulic chambers determine the flow versus piston position transfer function relationship. The shape and size of these components is determined by the desired flow requirements of a particular engine application. Flow through the flow tube is regulated by a computer-controlled electrical valve or a pair of check valves as well as by the size of the tube.
Moreover, the hydraulic fluid pressure for all of the actuators in an engine installation can be maintained, if desired, by selectively connecting all of the chambers via an electrical valve or check valve to a common reservoir. The check valve could be calibrated to let in more fluid when the system pressure drops below a preset level; alternatively, an electrical valve could let in more fluid when a pressure transducer sensed low pressure. Such a system would further be adapted to purge air intrusion and refill passages with hydraulic fluid as necessary.
According to a mechanical restraint embodiment of the present invention, a portion of the electromotive force produced by the opening coil is used to force a pin, transversely connected to the valve stem, though a guide track. The guide track includes a straight portion, where acceleration of the valve is desired, and a curved portion where deceleration of the valve is desired, (i.e. as the valve approaches the open or closed position respectively). By forcing the device to expend energy converting linear velocity to angular velocity, the valve may be brought to a controlled stop as it approaches the valve stop or seat, as the case may be. Moreover, as the pin enters the curved area of the channel, the valve necessarily turns, further contributing to the deceleration of the valve. Ultimately, the pin will be halted when the valve contacts the valve seat or an opening-stop.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.